Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$95.63	13.690%	$108.7217	$108.72	$108.70	$108.70
Purchase #2	$106.80	4.634%	$111.7491	$111.75	$111.75	$111.70
Purchase #3	$41.29	13.768%	$46.9748	$46.97	$46.95	$47.00
Purchase #4	$37.66	10.353%	$41.5589	$41.56	$41.55	$41.60
Purchase #5	$99.56	12.403%	$111.9084	$111.91	$111.90	$111.90
Purchase #6	$195.41	9.572%	$214.1146	$214.11	$214.10	$214.10
Purchase #7	$113.31	13.498%	$128.6046	$128.60	$128.60	$128.60
7 purchase totals =	$689.66		$763.6321	$763.62	$763.55	$763.60